It is known to burn refuse or the like on a grate made of a plurality of adjacent cylindrical rollers that are all rotated to mix and move the material being moved. Combustion air can pas through gaps in the rollers to gain access to the material being burned.
As described in U.S. Pat. No. 4,537,139 such a roller is comprised of a central shaft that is centered on and rotated about a longitudinal axis and that is provided externally with a plurality of normally T-section guides that in turn support an array of massive metallic grate bars. Each grate bars extends angularly over a small portion of the periphery of the roller and has ends fitted to the guides so that a plurality of bars together form a single ring and a stack of such rings form the roller.
The standard grate bar is, as mentioned, arcuate and of T-section, having relative to the roller axis a massive outer head forming the outer wear surface, and a radially inwardly projecting thin stiffening fin or leg. This is the basic grate-bar design used even in standard nonrolling grates as described in U.S. Pat. Nos. 2.372,260 and 2,257,295. The bars of the roller-type grate are mounted with some play so that they form the above-described air-flow gaps and so that they do not become wedged in place even when the entire grate is heated. This T-section configuration is even used in a step-type grate as described in Swiss patent 656,692 filed 14 January 1982 by B. Andreoli.
In German patent document 3,341,835 filed 19 November 1983 by E. Auchter asymmetrical bars are employed that can pivot considerably on the roller. The bars are basically of L-section with angled heads so that on the top of the roller the bars can lie at an angle with the outer surfaces of the heads laterally abutting and forming a cylinder while on the bottom of the roller they hang straight down with the heads separate and their outer surfaces extending at an angle to the roller axis. Such a system has the considerable advantage that the gaps formed by the heads at the top of the roll are open at a nonright angle to the outer roll surface so that the likelihood of the exiting gas impinging something on the roll surface are increased, but this arrangement has o the other hand been found likely to jamming in the perpendicular position assumed at the bottom of the roller.